Concept 1 Flashcards
evolution
change in populations over time,
makes descendants genetically different
Microevolution
Small scale evolution affecting a single population
Macroevolution
Large scale evolution affecting a species across populations
Natural selection
where organisms with the “best” traits
are favored and live longer and reproduce
Fitness
how well an organism can survive in its environment
Adaptation
an organism that can better survive in its
environment
Gene pool
The combined alleles of all individuals in a population
Genetic drift
random change in the allele frequency happens in the population
Gene flow
movement of genes
into or out of a population
Sexual selection
favors traits that potentially
decrease survival, but increase reproduction
Genetic equilibrium
no changes in the allele frequencies over time; evolution is not occurring
Explain the principles of natural selection
- There is an overproduction of offspring that leads to more organisms than resources, and thus creates competition.
- Within any population there will be variation.
- Some innate variations will allow organisms to better survive than others (adaptations).
- Over time, those traits should become more common because organisms with those traits will live longer and reproduce more, creating descendants with modifications from their ancestors
- over production and competition
- variation
- some variations live longer
- the ones that live longer reproduce
Write a real world example of evolution and how each principle was met
In a population of frogs, there is natural variation that exists in
their coloration. One particular season precipitation greatly decreases, and the foliage turns brown. The frogs that lack brown coloration can’t blend in and hide from their predators so they die before they can reproduce and pass on their traits. Brown coloration is favored and thus
an adaptation that should become more common over time if continually favored by the environment
Explain how diversity within a species has resulted
in an increase in fitness (survival of the fittest)
The more diverse a species is the less likely the entire
species can be eliminated by a sudden event.
- This is why sexual reproducers tend to be better at surviving in
regularly changing environments than asexual reproducers,
whose only source of variation is random mutation
List the different factors that contribute to genetic
variation and explain which is considered to be the “ultimate” source.
- Random mutations
- Ultimate source because the others don’t affect asexual
reproducers - Genetic recombination during meiosis
- Migration/gene flow
Explain what is meant by the phrase, “Individuals don’t
evolve, populations do.”
- Natural selection acts on traits that are heritable, not traits that
are acquired in a lifetime. - It is impossible for an individual to change their allele
frequencies. - Thus only populations can evolve because only within
populations do allele frequencies change over time.
Sketch pictures and explain the difference between the
three modes of selection
Directional favors one extreme, disruptive favors both
extremes, stabilizing favors the average
Describe at least three mechanisms of microevolution
- Genetic drift = random change in a population that often decreases variation
- Gene flow = the movement of genes into or out of a population, affecting the variation within the population
- Sexual selection (non-random mating) = favoring traits that increase reproduction over survival
Give an example of how genetic drift would have a
bigger impact on a smaller population than a larger
one.
- If a hurricane comes and flooding occurs and wipes out half of
a population of 1,000 insects, there are still 500 remaining and
most likely a decent amount of innate variation within them. - But if that same flooding occurs in a population of 100 insects
and only 50 survive, most likely a lot of variation was eliminated
and if those 50 only reproduce with each other, the traits that
exist in their alleles will be favored and the others will die out of
the population.
List the 5 conditions that must be met for evolution
to not occur.
- No mutations
- No natural selection
- LARGE population
- No migration
- Random mating
